rates and volumes used for jngemination would thus provide equal in-
semination doses for straws and pelletis in respect of numbers of
sperm.

The breeding efficiency was measured by 60-90 day non-return
percentages.

RESULTS. The results are given in Table 1. It appears that conception
Tates were 68.5% for 1993 inseminations with straws and 59.0% for
1872 inseminations with pellets, & highly significant difference. All
technicians except 1 had best results with straws, for 4 technicians
the differences were significant.

DISCUSSION. The results indicate that higher breeding efficiency may
Ye ensured by the straw method as compared to pellets. In a more re-
cent trial (4) a non-return percentage of 66.6 was obtained with
straws which was less than 3 percentage units lower than for fresh
gemen used on the day of collection which is the best result for
frozen semen ever reported from Denmark

By comparison of the results for the 14 technicians it appears
that their conception rates seem to vary more for pellets than for
straws. This suggestion is supported by the fact that the relation
between variances for pellet results and straiw results is lo.6™**.
The higher variation among technicians for pellets indicates the
existence of technician factors which have tended to impair the bree-
ding efficiency, whilst such factors have been less pronounced for
straws. The extra manipulations which are undertaken by the techni-
cians in the stable such as dilution of the pellet and the filling
of the insemination pipette as compared to the less complicated pro-
cedure by use of straws requiring less perfection on the technician's
part are possible explanations of the different results by the iwo
methods.

CONCLUSIONS. The trial has indicated that the straw method may ensure
higher conception rate than pellets, that the former requires less
perfection in connection with the insemination procedure and that it
provides more complete utilization of the semen.

(1) H. NAGASE and T. NIWA, 1963. Jap. J. An. Reprod., 9: 73-
(2) R. CASSOU, 1964. V. Int. Congr. Animal Reprod., Trento: 540-546.
(3)'R. CASSOU, 1964. C.R. Acad. Agric., 5o0: 881-887.

(4) H.C. ADLER, J.B. ANDERSEN and J.H. MEDING, 1968. Kgl. Vet.- og
Landboheo jsk., Inst. Sterilitetsforskn. Aarsberein., Keo-
benhavn. In press.

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